robbing the cradle

Verb

rob the cradle (third-person singular simple present robs the cradle, present participle robbing the cradle, simple past and past participle robbed the cradle)

1. (disapproving, idiomatic) To marry or become romantically involved with a much younger person, especially one from a younger generation.
   • The actress, 31, also pooh-poohs the notion that she's robbing the cradle with Timberlake, 22.2004 January 8, Karen Thomas, “Cameron won't pull a Britney”, in USA Today
2. (disapproving, idiomatic) To use a young person for a purpose inappropriate to their age.
   • They were ordered to the field, and their places filled by the Georgia "Reserves," an organization of boys under, and men over the military age. As General Grant aptly-phrased it, "They had robbed the cradle and the grave," in forming these regiments.1879, John McElroy, chapter 29, in Andersonville: A Story of Rebel Military Prisons